A method for the autocalibration of a turning tool for lenses is already known from DE 60 2005 003 012 T2. The method provides for the turning of a test piece with non-rotationally symmetrical geometry with a turning tool, the measurement of the cut geometry of the test piece in at least one section with an inclination in a direction of rotation about the turning axis of the work piece, the analysis of the thus obtained measurement data and the undertaking of compensatory regulation.
In U.S. Pat. No. 6,071,176, a calibration method for the driving axles of a grinding machine is described wherein the grinding tool is moved along two axes for the purpose calibrating the particular axis or for the purpose of measuring the particular axis error and a groove is generated, with a variation between the course of the machined groove and a desired measurement for the particular course of the axis being evaluated.
The lens machining unit known from DE 197 38 668 A1 has an end-milling cutter for the complete machining of the edge of a lens. A circumferential groove and a capping bevel are generated on the edge of the lens by means of the end-milling cutter. Alternatively, a combined tool which has various tool components of different forms, e.g. an end-milling cutter and a grinding disc, on a joint shaft is described. The various tool components are used one after the other for the purpose of machining the edge.
From US 2006/0276106 A1, a method for machining the edge of a lens is known, wherein a chamfer is first shaped and the achieved geometry is then measured for the purpose of agreement with the available geometry of the frame. No measurement of the lens takes place prior to the machining of the lens. The same applies in the case of DE 38 27 122 A1.
DE 198 04 455 C2 describes the measurement of the frame as well as the tool prior to the machining of the lens for the purpose of the agreement of the necessary tool movement. No measurement of the lens takes place prior to the machining of the lens.
DE 100 49 382 A1 describes optoelectronic measuring apparatus for the measurement of the geometry of the edges of lenses on the basis of the triangulation method for the purpose orienting the same for insertion in a spectacle frame. This kind of measurement takes place after the lens, including the frame, has been fully machined.
With regard to the precision of the surface, there are far fewer requirements with regard to the edges of lenses than with regard to the optical surfaces, that is to say the front and back themselves. They can, therefore, be brought to the final shape with the desired geometry by means of grinding and/or milling tools.
For the purposes of being received by suitably shaped frames, the edges of lenses sometimes have complex geometries, so that, particularly with the use of classical milling tools such as explained above, several procedural steps are required to produce such complex geometries. For the purpose of reducing machining times, grinding tools whose geometry is at least partially adapted to the complex edge shape RF are also used. As the lenses are made of plastic, tools have a very long life. The technical geometrical data of the tools used such as shaft length, radius, etc. are known or are manually measured prior to installation, so that the relative position of the clamped tool can be established by computer. The lens must only be held over the thus generated edge surface. Closed frames are usually also able to be adapted and are, in the case of plastic, heated for the purposes of inserting the lens, so that there is adaptation to the edge shape RF. The optical properties of the edge surface do not have to be taken into consideration.